From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5EAD1C47095 for ; Wed, 9 Jun 2021 06:58:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 465D56124C for ; Wed, 9 Jun 2021 06:58:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233568AbhFIHAL (ORCPT ); Wed, 9 Jun 2021 03:00:11 -0400 Received: from mail-pj1-f52.google.com ([209.85.216.52]:46819 "EHLO mail-pj1-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236354AbhFIHAL (ORCPT ); Wed, 9 Jun 2021 03:00:11 -0400 Received: by mail-pj1-f52.google.com with SMTP id pi6-20020a17090b1e46b029015cec51d7cdso800055pjb.5 for ; Tue, 08 Jun 2021 23:58:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=3yMOb1xLxlt9vST7EDzu6ffoTa7Kaw/NvhGe5FwxTv8=; b=VKDq6Sza/SZfP8YK4iJ6QBXnnU3PgVSRcV/S+60nuBvVQiV9RGVYHKjim/ZdFKG9zh XkI3IOXUdXJ0Pud8aKqHr2i4U58ntNevz/Da9bPCxz1YNVxAFC0xwfpLSu9sds5UjIRk 4d97dwK0mm+KKncnpGgq06zK3Ogz+b4aFzvul+m97o9p5WkERLhtsx0Wf+dSGew3mlY2 VRwjhc7DimC221yzQc3A08+ETOmlQ/RH5cdtX3BzdAUqOy9k6nxUadsRsrNo6BlLJkcT HdM9xK1pX0lUdhRN1291sSA7ZlvIQiSdtcbfChrIGgE7HnBxBIf4b/X+mkBh1Cz0c/aw XQzw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=3yMOb1xLxlt9vST7EDzu6ffoTa7Kaw/NvhGe5FwxTv8=; b=XAPPW4TZJMlPBZahQaeeu89tj3luEFMoSqtfVRPEqsu75gP5IrdF5QBFGhYQCxO3PJ Uo/3op98bGa+WdrBGMoioaDa+eOhc4HFE6oarBZFcSEC41/fk1pYTKcDMcHHcCFZZqtT 2OyuiSwnJgpDO0WWL+tD7qvbBIlj/Suk+QAvE2ETTlbXCuoN84kgd3aywWbwx5+As8Ud EI7KLIHP5+VWA36Fqpbu2ZTnmFHi0xGKYWDok52aYPFUkIFCSEoSKk9QsKKtIbWrGVP1 5vMK6PTu65TcoqHOE5Uy2wQ/wl7HtwLoWT94ZVUuKI3G9oFjqjPrG68kHmkJVEPDkbjL 4mdA== X-Gm-Message-State: AOAM531NcLHu2cJEms2VfcxeVIRTR3b+eIDxePafgFCUb1eq7hTJlcsh 3PS+Knf379azqIZJQpa33+jDbirZnrg= X-Google-Smtp-Source: ABdhPJxAM8aH7LOcdehqdJHoEya4BMCZq6QL/tbO/l7VWKWaITHu6Tys/I/f1Z7zS4HOYr8Anf6G6w== X-Received: by 2002:a17:902:e550:b029:110:3074:e7cd with SMTP id n16-20020a170902e550b02901103074e7cdmr4069425plf.25.1623221837287; Tue, 08 Jun 2021 23:57:17 -0700 (PDT) Received: from [10.7.3.1] ([133.130.111.179]) by smtp.gmail.com with ESMTPSA id x20sm12158002pfu.205.2021.06.08.23.57.14 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 08 Jun 2021 23:57:16 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.6\)) Subject: Re: [PATCH 2/2] block: support bio merge for multi-range discard From: Wang Shanker In-Reply-To: Date: Wed, 9 Jun 2021 14:57:11 +0800 Cc: Jens Axboe , Christoph Hellwig , linux-block@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <5D9A2192-E24F-4709-BA60-19219B6CEF55@gmail.com> References: <20210609004556.46928-1-ming.lei@redhat.com> <20210609004556.46928-3-ming.lei@redhat.com> To: Ming Lei X-Mailer: Apple Mail (2.3608.120.23.2.6) Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org > 2021=E5=B9=B406=E6=9C=8809=E6=97=A5 14:12=EF=BC=8CMing Lei = =E5=86=99=E9=81=93=EF=BC=9A >=20 > On Wed, Jun 09, 2021 at 11:05:59AM +0800, Wang Shanker wrote: >>=20 >>=20 >>> 2021=E5=B9=B406=E6=9C=8809=E6=97=A5 08:45=EF=BC=8CMing Lei = =E5=86=99=E9=81=93=EF=BC=9A >>>=20 >>> So far multi-range discard treats each bio as one segment(range) of = single >>> discard request. This way becomes not efficient if lots of small = sized >>> discard bios are submitted, and one example is raid456. >>>=20 >>> Support bio merge for multi-range discard for improving lots of = small >>> sized discard bios. >>>=20 >>> Turns out it is easy to support it: >>>=20 >>> 1) always try to merge bio first >>>=20 >>> 2) run into multi-range discard only if bio merge can't be done >>>=20 >>> 3) add rq_for_each_discard_range() for retrieving each = range(segment) >>> of discard request >>>=20 >>> Reported-by: Wang Shanker >>> Signed-off-by: Ming Lei >>> --- >>> block/blk-merge.c | 12 ++++----- >>> drivers/block/virtio_blk.c | 9 ++++--- >>> drivers/nvme/host/core.c | 8 +++--- >>> include/linux/blkdev.h | 51 = ++++++++++++++++++++++++++++++++++++++ >>> 4 files changed, 66 insertions(+), 14 deletions(-) >>>=20 >>> diff --git a/block/blk-merge.c b/block/blk-merge.c >>> index bcdff1879c34..65210e9a8efa 100644 >>> --- a/block/blk-merge.c >>> +++ b/block/blk-merge.c >>> @@ -724,10 +724,10 @@ static inline bool blk_discard_mergable(struct = request *req) >>> static enum elv_merge blk_try_req_merge(struct request *req, >>> struct request *next) >>> { >>> - if (blk_discard_mergable(req)) >>> - return ELEVATOR_DISCARD_MERGE; >>> - else if (blk_rq_pos(req) + blk_rq_sectors(req) =3D=3D = blk_rq_pos(next)) >>> + if (blk_rq_pos(req) + blk_rq_sectors(req) =3D=3D = blk_rq_pos(next)) >>> return ELEVATOR_BACK_MERGE; >>> + else if (blk_discard_mergable(req)) >>=20 >> Shall we adjust how req->nr_phys_segments is calculated in=20 >> bio_attempt_discard_merge() so that multiple contiguous bio's can >> be seen as one segment? >=20 > I think it isn't necessary, because we try to merge discard IOs first > just like plain IO. So when bio_attempt_discard_merge() is reached, it > means that IOs can't be merged, so req->nr_phys_segments should be > increased by 1. You are right. And by applying the series, I can confirm contiguous = bio's are getting merged into ~20M requests. It's much better than before. I=20= guess it might be the scheduler that prevents further merging. So it=20 seems that the root solution for raid456 is required since bio merging = cannot solve all the problem. Thanks again for your work. Cheers, Miao Wang